If they're a non-developer, the ability to clear all of the cookies (or data) for a given site should be adequate to cover their needs (and if they're a developer, obviously they'll just use Developer Tools > Application for individual cookie manipulation).
If a non-developer is in a situation where they need to delete a single cookie by name but deleting _all_ of that site's cookies would be ruinous for some reason, then something's horribly wrong.